A newly submitted plan to install a 16-foot-wide driveway to access an undeveloped 2.42-acre property in New Canaan that had been approved for a subdivision in 2014 will negatively affect the wetlands and watercourses that must be disturbed in order to create it, according to a consultant retained by one objecting neighbor.

“The driveway alignment as proposed is not adequate for the movement of emergency vehicles and should be denied on this basis alone. Additionally, there is a feasible and prudent alternative to the current proposal which is more environmentally friendly and less destructive to the wetland and adjacent upland areas.”

That alternative—described more fully below—would relocate the proposed driveway and change the infrastructure needed to address runoff.

The consultant’s report comes as the commission is scheduled to hear an application Monday night from property owner Hill Street-72 LLC.

According to a Feb. 17 project narrative from Steve McCallister of Wilton-based McChord Engineering Associates, the town already OK’d a 12-foot-wide driveway and pull-off area as part of its original 2014 approval for a 2-lot subdivision of the property.

It’s located about halfway along Hill Street, a windy road of 10 modest houses and condos that runs just above and roughly parallel to Route 123 for about 500 feet, east of Brushy Ridge Road.

After a neighbor raised concerns about the exact location of wetlands on the wooded property—it backs up to about a half-dozen Urban Street homes (see map below)—the applicant hired a second soil scientist and, with slightly different findings, redrew the boundary line in a way that resulted in an overall larger wetland area, according to McCallister.

“The original approval proposed a 12-foot wide driveway with a pull-off area and a stormwater drainage basin,” McCallister said. “This required a waiver from [the Planning & Zoning Commission] to deviate from the minimum required shared driveway width of 16 feet. The driveway would have 2-foot shoulders and adjacent grade sloping down to match existing grade. The installation of this driveway would require the disturbance of 930 square feet of inland wetlands.”

He continued: “The current proposal is to install a 16-foot wide driveway with 2-foot-wide shoulders. Stormwater runoff from this portion of driveway would discharge into concrete galleries beneath the driveway instead of a basin. Utilizing a retaining structure on the north side of the driveway reduces the overall area of disturbance on the property and reduces the area of wetland disturbance from 930 square feet to 720 square feet … for a reduction of 210 square feet.”

Yet, according to Trinkaus, the proposal would fill a “linear length” of wetlands from near Hill Street “to the upland area past the proposed open bottom culvert.”

“The filling in this area will have an adverse impact not only on the wetlands to be filled, but also on my client’s property as runoff will not be able to drain to the north unencumbered as currently occurs,” the consultant said in his letter to the commission.

He also raised concerns about the proposed driveway (saying it would act like a dam), allowable space for emergency vehicles, sanitary sewer line, proposed boulder wall, stormwater management and erosion and sediment control.

An attorney retained by opposing property owner Joseph Braccia—Joel Green of Bridgeport-based Green and Gross PC—said in a Feb. 22 letter to the commission that the applicant’s proposal would affect the wetlands’ ability to “support desirable wildlife, or other biological life, prevent flooding, supply water, assimilate waste, facilitate drainage [and] provide open space.”